<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
    .prefix{
        width: 100px;
        height: 100px;
        background-color: red;
        border-radius: 50%;
        -webkit-border-radius: 50%;
        -moz-border-radius: 50%;
        -o-border-radius: 50%;
        -ms-border-radius: 50%;
    }
</style>
<body>
    <div class="prefix">

    </div>
</body>
</html>